The albumin technique is the printing procedure that is most used in the 19th century. It was conceived around 1855 as the evolution of the previous printing technique that made use of salted paper. The only difference was the addition of albumin. The preparation of the binding agent consisted in adding some sodium chloride to the egg albumin and whisking it stiff. After allowing the “snow” to rest for several hours, the albumin that has settled at the bottom can be finally “collected”: this yields silver chloride that is sensitive to light. The paper is sensitised by making it float on the compound, and it can be printed after drying.
Prints produced with this technique can be recognised by the yellowing of the paper, by the loss of details in the lights and of surface glossiness. These prints are, in most cases, either framed or glued on stiff cardboard because they have a tendency to curl and roll up. A magnifying glass reveals the typical chapping caused by the poor elasticity of the binding agent.
The albumin print provides a suggestive view of Piazza Duomo by an unidentified author, with passers-by looking at the camera. The picture can be dated between 1885, the year when the arch-shaped Siemens electric lamps were installed, and 1896, when the equestrian monument to Victor Emanuel II was inaugurated.